This invention relates to signal encoding apparatus and methods.
In many digital systems, different configurations are required, wherein the particular configuration needs to be sensed by the digital system. If a large number of configurations is required, a binary encoding may be used where the number of options available is 2.sup.N, wherein N is the number of pins used. As the name suggests, binary systems have only two possible values per pin (usually high and low).
Often, configuration options for hardware are encoded using jumpers, the number of options being determined by the number of option pins. Often the number of pins available on an integrated circuit is at a premium due to cost and/or functionality requirements.
Three level (trinary or tri-state) encoding is known, where each pin has three possible values, namely high, low and mid. The electronic circuitry required to sense trinary levels is more complex than that required to sense binary levels, but often the extra complexity is outweighed by the reduced packaging costs in adopting trinary encoding. In particular, whereas four binary bits encodes sixteen possible values, four trinary bits encodes 81 possible values.
However, a disadvantage of conventional trinary encoding systems is that the encoding has a base of three, whereas most digital systems operate on a base of two (i.e. binary). This leads to undesirable technical complexities as well as difficulties for users not used to working to base three.
Accordingly, the invention seeks to provide an enhanced encoding which can provide more options than binary or trinary encoding, and is also compatible with existing systems.